Large curse a little offensive (9)
I believe the answer is:
loathsome
'offensive' is the definition.
(I know that offensive can be written as loathsome)
'large curse a little' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'curse' becomes 'oath' (synonyms).
'a little' becomes 'some' (both can mean a small amount).
'l'+'oath'+'some'='LOATHSOME'
(Other definitions for loathsome that I've seen before include "15 [ABHORRENT]" , "Repulsive" , "Disgusting, nauseating" , "Horrid" , "Hateful" .)